During the past thirty years, since the beginning of two-needle dialysis, many advances in dialysis technology have occurred. Since dialysis with two needles was begun, the dialyzer has increased in efficiency. The volume of blood delivered to the dialyzer to be processed per minute has increased from 200 cc/m to 400-600 cc/m. While this increase in efficiency reduces the amount of time dialysis takes, needle technology has not kept up with the overall level of dialysis technology.
Since needle technology has remained virtually unchanged in this field, the increased volume of blood causes an exponential increase of the positive pressure and velocity of the jet of blood exiting the venous needle. Using slightly larger needles has decreased the pressure and velocity of the blood jet to a certain extent. However, the use of larger needles is problematic since larger needles cause greater damage to a patient's skin and blood vessels.
Thus, it is necessary to design a new venous dialysis needle which will decrease the velocity, turbulence and shear stress the increased flow of blood causes.
Accordingly, one object of this invention is to decrease the velocity and pressure of the jet of blood exiting the needle's distal opening in order to decrease the shear stress on the endothelium inside the graft and in the venous anastomosis when operating in a dialysis set up to process 400-600 cc/m.
Another object of the invention is to decrease the turbulence of the blood reaching the venous anastomosis during dialysis.
Yet another object of the invention is to allow the use of needles of smaller diameter to decrease the trauma to the endothelium, graft, and skin.
Yet another object of the invention is to decrease the negative pressure of blood entering the arterial needle, reducing the risk of tearing the intima.
Yet another object of the invention is to decrease the risk of recirculation of previously processed blood from the venous needle back through the arterial needle and dialyzer.